The invention relates to an auto-hold function, i.e. an immobilizing function for temporarily holding an operationally ready motor vehicle in the stationary state by means of an electro-hydraulically, electro-pneumatically or electro-mechanically controlled service brake. Such an immobilizing function is known, for example, from DE 10 2008 020 844 A1.
In order to increase comfort and safety in vehicles, a wide variety of methods and devices are already known which are intended to serve to prevent an operationally ready motor vehicle from rolling away, in particular, but not necessarily, on gradients. In this context, when a brake pedal, or another operator control element which is provided therefor, is actuated in at least one operating state of the motor vehicle, a braking force is maintained or actively increased at at least one wheel of the vehicle. The braking force can also be increased here as a function of the degree of actuation of the pedal or the corresponding actuation of the operator control element. When the brake pedal is not actuated, the braking force is subsequently maintained up to a defined release condition, in particular until the accelerator pedal is actuated.
In addition to these immobilizing brake functions for temporarily holding an operationally ready motor vehicle in the stationary state, electromechanical holding functions are also known which can hold the vehicle, which has generally been parked, permanently in the stationary state. The brake pressure or the braking force (braking torque) for permanently holding the vehicle is maintained here by use of an additional mechanical parking brake device which can be activated by the driver at will by means of his own parking brake operator control element, in particular in the form of an electrical switch which can be actuated manually. An example of such a holding function or device is an electromechanical immobilizing brake (EMF) of the Applicant.
A wide variety of different entry conditions and/or triggering conditions are already provided for the activation and deactivation of the service brake within the scope of the abovementioned electrohydraulic, electropneumatic or electromechanical immobilizing brake functions for temporarily holding an operationally ready motor vehicle in the stationary state.
An immobilizing brake function for temporarily holding the vehicle is referred to below as an “auto-hold” function. An immobilizing brake function for permanently holding the vehicle is referred to below as a “parking brake” function.
The Applicant's vehicles include, to a certain extent, both a parking brake function and an auto-hold function. The two functions are currently each assigned to an operator control element for manually switching on and off. With respect to the functional capability of these two functions, reference is made, for example, to the online operating instructions of the BMW 5 Series, year of manufacture 2014 (online version for item number 0140 2 928 052-II/14).
The object of the invention is to reduce the costs for implementing an auto-hold function.
This and other objects are achieved by a method, a vehicle and an electronic control unit having a function module for controlling the auto-hold function and the parking brake function in a motor vehicle. The function module is configured such that it receives an electrical signal of the operator control element for switching the parking brake function on and off as an input signal, wherein when the parking brake function is switched on in the stationary state the auto-hold function is or can be activated simultaneously.
The invention is based on the main concept of implementing both a parking brake function and an auto-hold function with just a single common operator control element.
When the auto-hold function is activated, the vehicle is braked hard as soon as a stationary state of the vehicle is detected, in particular if the speed of the motor vehicle has undershot a predefined speed threshold which is tending toward zero. The activation of the auto-hold function can therefore already take place before stationary state. An activated auto-hold function occurs, as it were, in a standby state during travel and goes into a hard braking state in the stationary state of the vehicle. According to the prior art, until now a separate pushbutton key has been provided for activating or deactivating the auto-hold function. According to the invention, this pushbutton key should be dispensed with, and the activation or deactivation of the auto-hold function should be carried out by an operator control element (in particular a pushbutton key or switch) which is also used to switch the parking brake function on and off.
For this purpose, according to the invention, the operator control element is connected to an electronic control unit by which both the auto-hold function and the parking brake function can be controlled. For this purpose, the control unit is configured in such a way that, when the parking brake function is switched on in the stationary state, the auto-hold function is or can be activated simultaneously.
Furthermore, the control unit is configured in such a way that, when the accelerator pedal is actuated, the parking brake function is switched off automatically without actuation of the operator control element, but the auto-hold function remains activated.
In an alternative embodiment, when the parking brake function is switched on in the stationary state, the auto-hold function is deactivated. When the accelerator pedal is actuated, the parking brake function is switched off out of this state and the auto-hold function is activated.
In one development of the invention, the control unit is configured in such a way that when the parking brake function is switched off in the stationary state, the auto-hold function can also be deactivated by actuating the operator control element.
In a first alternative, the control unit is configured in such a way that when the operator control element is actuated in the stationary state, out of the state of a deactivated auto-hold function and a switched-off parking brake function, in a way which causes the parking brake to switch on in the stationary state (e.g. pulling on a pull/push switch as an operator control element), both functions are activated simultaneously.
In a second alternative, the control unit is configured in such a way that when the operator control element is actuated for the first time in the stationary state, out of the state of a deactivated auto-hold function and a switched-off parking brake function, in the way which causes the parking brake to switch on in the stationary state, firstly only the auto-hold function is activated. Then, when the operator control element is actuated again, the parking brake function is also switched on, wherein the auto-hold function remains activated.
This second alternative applies analogously to the switched-off process and deactivation process with corresponding actuation of the operator control element in a way which causes the parking brake to switch off in the stationary state (e.g. pressing on a pull/push switch as an operator control element).
In a first alternative, the control unit is further configured in such a way that when the operator control element is actuated during travel in a way which causes the parking brake to switch on in the stationary state (e.g. pulling on a pull/push switch as an operator control element), the auto-hold function is activated, in particular when the actuation of the operator control element is performed in a defined, comparatively short time or when no emergency braking function is connected to the actuation of the operator control element during travel.
In a second alternative, the control unit is further configured in such a way that when the operator control element is actuated during travel in a way which causes the parking brake to switch on in the stationary state, the auto-hold function cannot be activated in particular if an emergency brake function (e.g. by means of continuous pulling on a pull/push switch as an operator control element) is connected to the actuation of the operator control element during travel.
In a third alternative, the control unit is further configured in such a way that when the operator control element is actuated during travel in a way which causes the parking brake to switch on in the stationary state, the auto-hold function can be activated if the actuation of the operator control element is performed in a defined, comparatively short time, and that, after the expiry of this time, a further actuation of the operator control element causes an emergency braking function.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.